Clive Shrubsole

Home energy efficiency and radon related risk of lung cancer: modelling study.

Objective To investigate the effect of reducing home ventilation as part of household energy efficiency measures on deaths from radon related lung cancer. Design Modelling study. Setting England. Intervention Home energy efficiency interventions, motivated in part by targets for reducing greenhouse gases, which entail reduction in uncontrolled ventilation in keeping with good practice guidance. Main outcome measures Modelled current and future distributions of indoor radon levels for the English housing stock and associated changes in life years due to lung cancer mortality, estimated using life tables. Results Increasing the air tightness of dwellings (without compensatory purpose-provided ventilation) increased mean indoor radon concentrations by an estimated 56.6%, from 21.2 becquerels per cubic metre (Bq/m3) to 33.2 Bq/m3. After the lag in lung cancer onset, this would result in an additional annual burden of 4700 life years lost and (at peak) 278 deaths. The increases in radon levels for the millions of homes that would contribute most of the additional burden are below the threshold at which radon remediation measures are cost effective. Fitting extraction fans and trickle ventilators to restore ventilation will help offset the additional burden but only if the ventilation related energy efficiency gains are lost. Mechanical ventilation systems with heat recovery may lower radon levels and the risk of cancer while maintaining the advantage of energy efficiency for the most airtight dwellings but there is potential for a major adverse impact on health if such systems fail. Conclusion Unless specific remediation is used, reducing the ventilation of dwellings will improve energy efficiency only at the expense of population wide adverse impact on indoor exposure to radon and risk of lung cancer. The implications of this and other consequences of changes to ventilation need to be carefully evaluated to ensure that the desirable health and environmental benefits of home energy efficiency are not compromised by avoidable negative impacts on indoor air quality.

Impact of climate change on the domestic indoor environment and associated health risks in the UK

There is growing evidence that projected climate change has the potential to significantly affect public health. In the UK, much of this impact is likely to arise by amplifying existing risks related to heat exposure, flooding, and chemical and biological contamination in buildings. Identifying the health effects of climate change on the indoor environment, and risks and opportunities related to climate change adaptation and mitigation, can help protect public health. We explored a range of health risks in the domestic indoor environment related to climate change, as well as the potential health benefits and unintended harmful effects of climate change mitigation and adaptation policies in the UK housing sector. We reviewed relevant scientific literature, focusing on housing-related health effects in the UK likely to arise through either direct or indirect mechanisms of climate change or mitigation and adaptation measures in the built environment. We considered the following categories of effect: (i) indoor temperatures, (ii) indoor air quality, (iii) indoor allergens and infections, and (iv) flood damage and water contamination. Climate change may exacerbate health risks and inequalities across these categories and in a variety of ways, if adequate adaptation measures are not taken. Certain changes to the indoor environment can affect indoor air quality or promote the growth and propagation of pathogenic organisms. Measures aimed at reducing greenhouse gas emissions have the potential for ancillary public health benefits including reductions in health burdens related heat and cold, indoor exposure to air pollution derived from outdoor sources, and mould growth. However, increasing airtightness of dwellings in pursuit of energy efficiency could also have negative effects by increasing concentrations of pollutants (such as PM2.5, CO and radon) derived from indoor or ground sources, and biological contamination. These effects can largely be ameliorated by mechanical ventilation with heat recovery (MVHR) and air filtration, where such solution is feasible and when the system is properly installed, operated and maintained. Groups at high risk of these adverse health effects include the elderly (especially those living on their own), individuals with pre-existing illnesses, people living in overcrowded accommodation, and the socioeconomically deprived. A better understanding of how current and emerging building infrastructure design, construction, and materials may affect health in the context of climate change and mitigation and adaptation measures is needed in the UK and other high income countries. Long-term, energy efficient building design interventions, ensuring adequate ventilation, need to be promoted.

100 Unintended consequences of policies to improve the energy efficiency of the UK housing stock

As a major sector contributing to the UK’s greenhouse gas (GHG) emissions, housing is an important focus of government policies to mitigate climate change. Current policy promotes the application of a variety of energy efficiency measures to a diverse building stock, which will likely lead to a wide range of unintended consequences. We have undertaken a scoping review identifying more than 100 unintended consequences impacting building fabric, population health and the environment, thus highlighting the urgent need for government and society to reconsider its approach. Many impacts are connected in complex relationships. Some are negative, others possibly co-benefits for other objectives. While there are likely to be unavoidable trade-offs between different domains affected and the emissions reduction policy, a more integrated approach to decision making could ensure co-benefits are optimised, negative impacts reduced and trade-offs are dealt with explicitly. Integrative methods can capture this complexity and support a dynamic understanding of the effects of policies over time, bringing together different kinds of knowledge in an improved decision-making process. We suggest that participatory systems dynamics with multi/inter-disciplinary stakeholders is likely to offer a useful route forward, supporting cross-sectorial policy optimisation that places reducing housing GHG emissions alongside other housing policy goals.

Health effects of home energy efficiency interventions in England: a modelling study

Objective To assess potential public health impacts of changes to indoor air quality and temperature due to energy efficiency retrofits in English dwellings to meet 2030 carbon reduction targets. Design Health impact modelling study. Setting England. Participants English household population. Intervention Three retrofit scenarios were modelled: (1) fabric and ventilation retrofits installed assuming building regulations are met; (2) as with scenario (1) but with additional ventilation for homes at risk of poor ventilation; (3) as with scenario (1) but with no additional ventilation to illustrate the potential risk of weak regulations and non-compliance. Main outcome Primary outcomes were changes in quality adjusted life years (QALYs) over 50 years from cardiorespiratory diseases, lung cancer, asthma and common mental disorders due to changes in indoor air pollutants, including secondhand tobacco smoke, PM2.5 from indoor and outdoor sources, radon, mould, and indoor winter temperatures. Results The modelling study estimates showed that scenario (1) resulted in positive effects on net mortality and morbidity of 2241 (95% credible intervals (CI) 2085 to 2397) QALYs per 10 000 persons over 50 years follow-up due to improved temperatures and reduced exposure to indoor pollutants, despite an increase in exposure to outdoor-generated particulate matter with a diameter of 2.5 μm or less (PM2.5). Scenario (2) resulted in a negative impact of −728 (95% CI −864 to −592) QALYs per 10 000 persons over 50 years due to an overall increase in indoor pollutant exposures. Scenario (3) resulted in −539 (95% CI −678 to -399) QALYs per 10 000 persons over 50 years follow-up due to an increase in indoor exposures despite the targeting of pollutants. Conclusions If properly implemented alongside ventilation, energy efficiency retrofits in housing can improve health by reducing exposure to cold and air pollutants. Maximising the health benefits requires careful understanding of the balance of changes in pollutant exposures, highlighting the importance of ventilation to mitigate the risk of poor indoor air quality.

Integrated decision-making about housing, energy and wellbeing: a qualitative system dynamics model

BackgroundThe UK government has an ambitious goal to reduce carbon emissions from the housing stock through energy efficiency improvements. This single policy goal is a strong driver for change in the housing system, but comes with positive and negative “unintended consequences” across a broad range of outcomes for health, equity and environmental sustainability. The resulting policies are also already experiencing under-performance through a failure to consider housing as a complex system.This research aimed to move from considering disparate objectives of housing policies in isolation to mapping the links between environmental, economic, social and health outcomes as a complex system. We aimed to support a broad range of housing policy stakeholders to improve their understanding of housing as a complex system through a collaborative learning process.MethodsWe used participatory system dynamics modelling to develop a qualitative causal theory linking housing, energy and wellbeing. Qualitative interviews were followed by two interactive workshops to develop the model, involving representatives from national and local government, housing industries, non-government organisations, communities and academia.ResultsMore than 50 stakeholders from 37 organisations participated. The process resulted in a shared understanding of wellbeing as it relates to housing; an agreed set of criteria against which to assess to future policy options; and a comprehensive set of causal loop diagrams describing the housing, energy and wellbeing system. The causal loop diagrams cover seven interconnected themes: community connection and quality of neighbourhoods; energy efficiency and climate change; fuel poverty and indoor temperature; household crowding; housing affordability; land ownership, value and development patterns; and ventilation and indoor air pollution.ConclusionsThe collaborative learning process and the model have been useful for shifting the thinking of a wide range of housing stakeholders towards a more integrated approach to housing. The qualitative model has begun to improve the assessment of future policy options across a broad range of outcomes. Future work is needed to validate the model and increase its utility through computer simulation incorporating best quality data and evidence. Combining system dynamics modelling with other methods for weighing up policy options, as well as methods to support shifts in the conceptual frameworks underpinning policy, will be necessary to achieve shared housing goals across physical, mental, environmental, economic and social wellbeing.

The Effect of Party Wall Permeability on Estimations of Infiltration from Air Leakage

Abstract The importance of reducing adventitious infiltration in order to save energy is highlighted by the relevant building standards of many countries. This operational infiltration is often inferred via the measurement of the air leakage rate at a pressure differential of 50 Pascals. Some building codes, such as the UK’s Standard Assessment Procedure, assume a simple relationship between the air leakage rate and mean infiltration rate during the heating season, the so-called leakage-infiltration ratio, which is scaled to account for the physical and environmental properties of a dwelling. The scaling does not take account of the permeability of party walls in conjoined dwellings and so cannot be used to differentiate between the infiltration of unconditioned ambient air that requires heating, and conditioned air from an adjacent dwelling that does not. This article evaluates the leakage infiltration ratio afresh using a theoretical model of adventitious infiltration for a conjoined dwelling. The model is used to predict the mean infiltration rate during the heating season for an apartment and a terraced house located in 14 different UK cities for two extreme assumptions of party wall permeability. The first assumption is that party walls are permeable - this results in a predicted leakage-infiltration ratio that is significantly greater than that used by building codes to evaluate the energy and environmental performance of dwellings. The second assumption is that party walls are impermeable - this results in a predicted leakage-infiltration ratio close to that used by building codes. Knowledge of party wall permeability is not provided by a standard measurement of air leakage but is shown to be vital for making informed decisions on the implementation of energy efficiency measures. These findings have significant energy and health implications and should be of great interest to the policy makers of any country with a large number of conjoined dwellings.

Understanding and mitigating overheating and indoor PM2.5 risks using coupled temperature and indoor air quality models

Indoor temperature and air quality in dwellings are closely coupled. Differences between the indoor temperature and the temperature outside and in adjoining zones can influence airflow due to the stack effect, whilst changes in ventilation can cause changes in indoor pollution and temperature. This paper demonstrates the relationship between an indoor air pollutant, PM2.5, and temperature in UK domestic building archetypes using the dynamic thermal and contaminant modelling capabilities of EnergyPlus 8.0 under various UK Climate Projections 2009 (UKCP09) scenarios (current, current ‘hot’, 2050 High Emissions and 2050 High Emissions ‘hot’), with both internal and external PM2.5 sources. Results indicate that flats have 0.7–0.8 times as much outdoor PM2.5 infiltrating indoors compared to detached dwellings, but 1.8–2.8 times more PM2.5 from indoor sources. During hot periods, temperature-dependent window opening increases exposure to outdoor PM2.5, meaning that as temperatures rises, dwelling occupants will become exposed to relatively higher levels of outdoor PM2.5 and lower levels of indoor PM2.5 due to the need to increase dwelling ventilation. The practical implications for government and designers and possible policy implications of this research are discussed. Practical applications : This paper demonstrates how an increase in summertime ventilation is necessary in UK homes to reduce overheating risks due to climate change and energy-efficient building retrofits. This, in turn, will lead to a change in the profile of indoor air pollution exposure, with greater exposure to pollution from outdoor sources and reduced exposure to pollution from indoor sources. Roof insulation and trickle vents reduce overheating risk, whilst increased use of mechanical ventilation heat recovery systems in the UK is encouraged, as it offers the co-benefits of cooling through increased ventilation, energy recovery and the potential to reduce indoor pollution levels.

Overheating in English dwellings: comparing modelled and monitored large-scale datasets

ABSTRACT Monitoring and modelling studies of the indoor environment indicate that there are often discrepancies between simulation results and measurements. The availability of large monitoring datasets of domestic buildings allows for more rigorous validation of the performance of building simulation models derived from limited building information, backed by statistical significance tests and goodness-of-fit metrics. These datasets also offer the opportunity to test modelling assumptions. This paper investigates the performance of domestic housing models using EnergyPlus software to predict maximum daily indoor temperatures over the summer of 2011. Monitored maximum daily indoor temperatures from the English Housing Survey’s (EHS) Energy Follow-Up Survey (EFUS) for 823 nationally representative dwellings are compared against predictions made by EnergyPlus simulations. Due to lack of information on the characteristics of individual dwellings, the models struggle to predict maximum temperatures in individual dwellings and performance was worse on days when the outdoor maximum temperatures were high. This research indicates that unknown factors such as building characteristics, occupant behaviour and local environment makes the validation of models for individual dwellings a challenging task. The models did, however, provide an improved estimate of temperature exposure when aggregated over dwellings within a particular region.

Impacts of energy efficiency retrofitting measures on indoor PM2.5 concentrations across different income groups in England: a modelling study

As part of an effort to reduce carbon emissions in the UK, policies encouraging the energy-efficient retrofit of domestic properties are being implemented. Typical retrofits, including installation of insulation and double glazing can cause tightening of the building envelope which may affect indoor air quality (IAQ) impacting occupant health. Using the example of PM2.5 (an airborne pollutant with known health impacts), this study considers the influence of energy-efficient retrofits on indoor PM2.5 concentrations in domestic properties both above and below the low-income threshold (LIT) for a range of tenancies across England. Simulations using EnergyPlus and its integrated Generic Contaminant model are employed to predict indoor PM2.5 exposures from both indoor and outdoor sources in building archetypes representative of (i) the existing housing stock and (ii) a retrofitted English housing stock. The exposures of occupants for buildings occupied by groups above and below the LIT are then estimated under current conditions and following retrofits. One-way ANOVA tests were applied to clarify results and investigate differences between the various income and tenure groups. Results indicate that all tenures below the LIT experience greater indoor PM2.5 concentrations than those above, suggesting possible social inequalities driven by housing, leading to consequences for health.

Simulation of pollution transport in buildings: the importance of taking into account dynamic thermal effects

The recent introduction of the Generic Contaminant Model in EnergyPlus allows for the integrated modelling of multizone contaminant and dynamic thermal behaviour within a single simulation package. This article demonstrates how dynamic thermal simulation can modify pollutant transport within a building. PM2.5 infiltration from the external to internal environment under dynamic thermal conditions is compared in CONTAM, EnergyPlus 8.0, and Polluto, an in-house pollutant transport model developed in EnergyPlus 3.1. The influence of internal temperature on indoor PM2.5 levels is investigated by comparing results from standard CONTAM simulations and dynamic thermal EnergyPlus 8 simulations. Circumstances where the predictions of such models can diverge are identified. Practical application: This technical note compares the performance of a new indoor air quality model in EnergyPlus, an EnergyPlus in-house model (Polluto), and an established model (CONTAM). The work then compares the results of indoor air quality models under static and dynamic internal temperature conditions, and demonstrates how predicted indoor pollution levels may deviate significantly if an inappropriate indoor temperature is used. Practically, the work provides confidence in the new models, as well as demonstrating the importance of having a good understanding of the thermal behaviour of a building when modelling indoor air quality.